344. 反转字符串
https://leetcode.cn/problems/reverse-string/description/

class Solution {
public:
    void reverseString(vector<char>& s) {
        int i=0;
        int j=s.size()-1;
        while(i!=j)
        {
            swap(s[i],s[j]);
            i++;
            j--;
        }
    }
};